1. Field of the Invention
The present invention generally relates to a semiconductor device and a method of producing the semiconductor device. More particularly, the present invention relates to a semiconductor device suitable for mounting a semiconductor chip which generates heat during an operation and to a method producing such a semiconductor device.
2. Description of the Related Art
As the density of a semiconductor chip has increased in recent years, the number of terminals in a semiconductor chip has increased accordingly. Also, there is a growing tendency for a semiconductor chip to consume a large amount of electric power and to generate a large amount of heat.
In the meantime, electric devices mounted with semiconductor chips have rapidly become smaller, and there is a demand for smaller semiconductor chips. Therefore, it is necessary to develop a semiconductor chip which is small and thin, even if the number of terminals is large.
FIG. 1 illustrates a conventional fine-pitch type semiconductor device 1. This semiconductor device 1 has a package structure called FBGA (Fine-pitch Ball Grid Array). This structure includes a semiconductor chip 2, a wiring board 3, solder balls 7, and a sealing resin 8.
The semiconductor chip 2 has a high density, and is fixed with an adhesive 5 onto the upper surface of the wiring board 3, which functions as an interposer. The wiring board 3 is a printed wiring board or a flexible printed board (in FIG. 1, a flexible printed board is shown). The wiring board 3 has a wiring layer 4 formed on a polyimide tape. The wiring layer 4 and the semiconductor chip 2 are electrically connected by a wire 6.
An opening is formed in a predetermined position of the polyimide tape, and the solder balls 7 are bonded to the wiring layer 4 through the opening. Thus, the semiconductor chip 2 is electrically connected to the solder balls 7 as external connecting terminals via the wiring layer 4.
The sealing resin 8 is molded to cover the semiconductor chip mounting surface of the wiring board 3, so as to protect the semiconductor chip 2, the wiring layer 4, and the wire 6.
In the semiconductor device 1 shown in FIG. 1, a fine pitch is obtained by arranging the solder balls 7 in a grid pattern on the wiring board 3, so that the semiconductor device 1 is compatible with the large number of terminals.
As a semiconductor chip has a higher density, the semiconductor chip generates a larger amount of heat. In the semiconductor device 1, the only heat releasing passage for the heat generated from the semiconductor chip 2 is the sealing resin 8 or the wiring board 3. However, the resin material used for the sealing resin 8 and the wiring board 3 is poor in thermal conductivity. The heat releasing efficiency of the semiconductor device 1 is low, and the heat generated from the semiconductor chip 2 stays inside the device. As a result, the semiconductor chip 2 is overheated, and causes a faulty operation.